Resins used for electric and electronic parts have been provided with flame retardancy by flame retardants depending on the use or the portion to which a resin is applied. As the flame retardant, for example, bromine-based flame retardants, phosphorus-based flame retardants, inorganic flame retardants, and silicone-based flame retardants are known. For example, a polybutylene terephthalate resin, which is widely used in copiers, contains a phosphorus-based flame retardant mixed therein to have a flame retardancy of V-2 to V-0 of the standard UL-94, depending on the use.
Meanwhile, from the viewpoint of reducing the consumption of petroleum resources, biomass-derived resins prepared from plants have received attention. For example, polylactic acid is produced from starch such as corn starch. The biomass-derived resins are improved in strength and flame retardancy by an alloy with a petroleum-derived resin or an additive and are actually used in the housings of copiers and other apparatuses.
However, in flame retardants, petroleum-derived materials are still used, and development of a flame retardant from a renewable resource such as a plant is being demanded from the above-described viewpoints.
PTL 1 describes tannin as a flame retardant obtained from a plant. PTL 2 describes potassium hydrogen tartrate as a flame retardant obtained from a plant.
Unfortunately, these flame retardants could not realize a high flame retardancy in accordance with the standard UL-94 for being used in members of copiers when they are added to polybutylene terephthalate. This is believed to be caused by low compatibility with resins due to hydrophilicity of the tannin and potassium hydrogen tartrate.